The electric and magnetic properties study of nanocrystalline triple perovskite Sr₃Co₂WO₉ prepared by the modified sol-gel route

Polar perovskite materials have attracted extensive attention due to the coexistence of magnetic ground state and semiconductor band gap within the same material. For the first time triple perovskite Sr₃Co₂WO₉ has been synthesized in the nanocrystalline form with an average crystallite size of 23 nm using a modified aqueous citrate sol-gel method. The crystal structure of Sr₃Co₂WO₉ is cubic at the room temperature, space group Fm-3m with with lattice parameter a= 7.9073(6) Å. The formation of Sr₃Co₂WO₉ was studied by cyclic voltammetry, UV/Vis spectroscopy and in situ X-ray diffraction method subsequently analysed by the Rietveld analysis. The detected hysteresis loops reveal ferrimagnetic ordering with Curie temperature of 144 K. The measured effective magnetic moment of 3 mB is close to the expected value for rarely observed intermediate spin S = 1 but can also be explained as a combination of HS (40 %) Co³⁺ and LS (60 %). The compound exhibits the semiconducting properties with the optical band gaps equal to 3.52 eV (indirect) and 3.76 eV (direct), respectively, calculated from UV/Vis absorption spectrum using the Tauc method. Semiconducting nature was also confirmed by AC conductivity measurements, which is between 10⁻⁵ and 10⁻⁴ Ω⁻¹ cm⁻¹. The frequency dependent dielectric constant was explained by employing the Maxwell-Wagner model. The frequency dependent AC conductivity follows the universal Jonscher's power law. This material could be a good candidate for implementation as a constituent for devices where its semiconducting properties would be spin controlled. (author)